Organic electroluminescent elements are drawing attention in applications such as planar light sources. In an organic electroluminescent element, an organic thin film is provided between a cathode and an anode; a voltage is applied between the cathode and the anode; excitons are created; and the light emitted when the excitons undergo radiative deactivation is utilized. Materials having relatively low conductivities such as, for example, ITO (Indium Tin Oxide) are used as the anode.
In organic electroluminescent elements having large surface areas, the contact portions for applying a voltage to the element often are provided at the periphery of the light emitting unit. Therefore, the voltage applied to the element decreases and the luminance decreases at the light emitting unit distal to the contact portion mainly due to a potential drop caused by the resistance of the anode; and the brightness becomes nonuniform.
Conversely, it is conceivable to employ a measure that adds, for example, a metal supplemental interconnect having a mesh configuration on the anode. However, in such a case, the opening ratio decreases and the luminance decreases.
On the other hand, JP-A 2005-158371 (Kokai) discusses an organic EL element having a configuration in which an anode, an organic layer, and a cathode are stacked sequentially on a transparent substrate; this stacked structural body is covered with a sealing film; an anode terminal is provided on the sealing film; an opening is provided in the sealing film; the cathode is exposed at the opening and a cathode terminal is formed; multiple through-holes are provided to pierce the sealing film, the cathode, and the organic layer in portions where the opening of the sealing film is not provided; and an anode terminal is electrically connected to the anode via the through-holes.
Using such conventional art, the potential drop of the anode cannot be suppressed sufficiently; and there is room for improvement to realize a uniform and bright illumination device having a large surface area with high productivity.